VEXnet and Motor Current Draw

Hello, I was at a competition and our robot had occasional VEXnet connection issues. It only disconnected for a couple seconds at a time, usually restoring connection as soon as the robot stopped moving. I observed that these connection issues usually only occurred during intense matchplay when the robot was making a lot of quick maneuvers in a very small window of time.

Can motors suddenly drawing a large amount of current cause VEXnet to lose connection? We have a 6-motor 393 1.6:1 (high speed) drive, with four motors plugged directly into the cortex and 2 into the power expander, so hard maneuvering can draw a lot of current from the cortex battery.

Probably, that’s the reason (well, one of them) we have a backup battery. Was your backup battery connected?

What was the state of your backup battery? Fully charged and plugged in, low/dead and plugged in, or not plugged in at all?

EDIT: jpearman beat me… :slight_smile:

It was not, our 9v battery became a 2v battery a while back and we never got around to replacing it, so we haven’t been using it.

I believe the purpose of the 9v battery is to keep the microprocessor(s?) and VEXnet equipment running in event of low current from the 7.2v battery. This results in maintaining connection in event of brownout-like conditions.

As a side note: VEX Toss Up rules require a charged backup battery to be connected… (<R13c>) :wink: This is probably the most commonly broken rule at any tournament.

Do you really want to bother enforcing that? Tell teams to do it, sure. Explain why they should. But when it’s the last finals match of the day, and their backup battery is dead do you expect the referees to say “Sorry, your otherwise perfect robot can’t compete anymore?”

I think a more commonly broken rule is the one about repositioning while touching a grey tile. But that’s a whole different discussion.

I personally think pinning is the most commonly broken rule.

Edit: When I say pinning I mean pinning and trapping; they go hand in hand.

What do you mean, haven’t gotten around to it! That was in gateway, two years without a backup battery, and don’t disagree with me because I was on your team back then.

We had a backup battery again last year and another new one at the beginning of this year but it was drained earlier this season and never replaced because we don’t have an extra and no one has run to the store to get one since then.

When you make posts like this, I suggest you consider that information from two years ago may be out of date and no longer relevant.

Sorry, I thought I asked you last year and you said you still didn’t have a backup. Either I misunderstood you or you got one since then. I guess you got a new one but it ran out too.

I can agree with this statement.

It doesn’t matter at all if people running an event “want” to enforce it. It is a VRC rule and at a VRC tournament, it should be enforced. At small scrimmages, it doesn’t much matter, but at official tournaments that are giving away qualification spots (to the World Championship or a State/Regional Championship), all teams should be expected to abide by all of the rules. It doesn’t matter whether you think it is important or not, or what you believe the “intent” of the rule is.

Now, I can agree with you that in my opinion it seems like a rather dumb rule, but there are plenty of other rules that are similarly trying to protect teams from their own “stupidity”, so to speak. Although, with this one I believe that it was meant to eliminate some of the questions as to whether or not VEXnet connection issues were due to a competition field problem, or just a problem with a specific robot.


Pinning is not a rule.

Maintaining a pin or trap for extended periods of time is against the rules.

Up until the point that a person is told to back off they are not breaking a rule. The act of pinning is not against the rules in and of itself.

Okay let’s clarify. I meant “The pinning and trapping rules are the most violated rules.” I am well aware of their specifics.